The term “telecine” refers to the process of generating a television signal or at least a video signal from cinematographic film, i.e., generally speaking film to video conversion. A telecine machine converts images, and possibly sound and/or other cinematographic information, that are recorded on film into a video format. This video signal may be subsequently recorded on another medium such as on videotape by using for example a video tape recorder film. The resultant video signal, however, may contain ancillary information not recorded on film. For example, in the case where audio is not recorded on the film, an audio signal may be received into an auxiliary input on the telecine machine and incorporated into the video signal produced by the telecine machine. The images are converted into video and supplemented with audio to produce a video signal that includes both images and the sounds. Other information not recorded on film but possibly incorporated into the resultant video signal include e.g., close captioning.
When television first became popular, the state of technology was such that a device to convert images recorded on film into video was quite large and heavy. Since the video tape recorder for storing video electronically was not available until after a number of years of commercial TV broadcasting, the telecine device was designed to be used in a broadcast studio connected to the TV broadcast transmission system. Subsequent designs of full-featured telecine devices have followed the original concept of a large system that is permanently installed.
To transfer film onto video, the telecine device is typically loaded with a spool of film which uses its transport mechanism to move the film across a beam of light. Light that passes through the film is directed through lenses, filters and other optical elements towards a series of sensors that convert optical images of consecutive portions of the film into video signals. Outputs from the sensors are processed in a number of ways to improve or modify the video image, such processors being used, for example, to enhance, color correct, filter, anti-alias, pan and scan, crop and compress the new version of the image. The telecine device provides its data in a particular analog or digital format suitable for storage or further processing or display or conversion into a video signal on an output port and continues to do so until the entire spool of film has been processed or until the telecine operator terminates the process. Some telecine devices are equipped with local memory storage that can hold data corresponding to scanned film frames for reference or for additional processing.
Telecine devices typically operate at a real-time (e.g., 24 frames-per-second) or slower rate. It is common to use 24 frames of film to record one second of motion. The operating rate of the telecine device is typically at or less than the real-time rate, even for films that are recorded at a faster rate than the real-time rate. Devices (i.e., video recorders) coupled to the output of the telecine device expect the telecine device to provide video signals conforming to a particular video standard.
Popular video standards include the National Television System Committee (NTSC) standard in America and Asia, the Phase Alternating Line (PAL) standard in most European countries, and the Sequential Couleur Avec Memoire (SECAM) standard in France. Each video standard defines a particular resolution (i.e., number of lines per frame) and a particular number of frames per second. Each video standard is incompatible with the other. For example, a European video conforming to the PAL standard cannot be played on an American videocassette player or shown on American television that expects the video to conform to the NTSC standard. The timing specifications are different for different video standards. To maintain the proper timing for a desired video standard, the telecine device typically operates at the real-time or slower rate. When the telecine device is operating at the slower than real-time rate, the outputs can be buffered until there is a reasonable collection of video information to start or resume a video recording conforming to the desired video standard. In order to match 24 frames-per-second to NTSC, extra frames are added.
Ancillary information, such as audio and metadata information, is synchronized with the video images. Ancillary information can be provided by the film, a digital file or a peripheral device connected to the telecine device. Pitch converters can adjust the audio speed to match the conversion rate of the telecine device. Film rates and video rates differ. Pitch converters resynchronize the audio with the video so that sound appears to coincide with motion. For example, when 24 frames-per-second film is converted to 29.97 NTSC video, the audio speed must be changed to match the motion in the eventual playback of the resulting video. Some pitch converters can adjust the audio speed in the −25% to +33% range.